Turbulent heat transfer in channels with irregular roughness

What is it about?

It is well known that rough surfaces affect turbulent flows significantly. How such surfaces affect turbulent heat transfer is less well understood. To gain more insight, we have performed a series of direct numerical simulations of turbulent heat transfer in a channel flow with grit-blasted surfaces. The heat transfer modification by wall roughness is analysed in detail. The failure of the Reynolds analogy in fully rough conditions can be directly related to the difference between the wall functions for the velocity and the scalar mean profiles.

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Why is it important?

In engineering, heat transfer often occurs at surfaces which are not hydrodynamically smooth. Non-smooth surfaces are typically created due machining, fouling or corrosion. By understanding the relation between surface topology and turbulent heat transfer, we may be able to optimize heat transfer equipment.